This invention relates to boxes and cartons for shipping, storage, or display, and is more particularly concerned with boxes formed of corrugated paper board or equivalent sheet materials where a filler is sandwiched between an inner liner and an outer liner. The invention relates not only to boxes and trays made of corrugated paper starting material, but also to boxes of other flat sheet material where a filler is sandwiched between outer and inner liners. An alternative filler can be, e.g., cellulose fiber or a foamed polymer. The liners can be paper, or in some cases a plastic film or metallized plastic film. The sheet material can also be wrapped chipboard.
Shallow boxes are often employed for carrying small items of merchandise, such as cosmetics, handkerchiefs, or packages of photographic film. The box is required to be lightweight but substantially rigid, and must have a neat and trim appearance. A layer of paper serves as the wrapper or liner, and can be plain or printed paper. The liner should continue over the side wall of the box covering all sides and edges so that the filler is entirely concealed. Any text, labels, or decoration printed on the liner should not be cut through. High stacking strength is desirable.
A typical cardboard box structure of this type is shown in U.S. Pat. No. 2,634,046, which provides a double-thickness side wall for added rigidity. In this case, the back is dadoed to form two channels parallel to the edge defining the folds where the side wall is formed. This results in rounded edges on the lower and upper parts of the side walls.
Other boxes where the folds occur at dadoed grooves are shown, e.g., in U.S. Pat. No. 2,932,439, and U.S. Pat. No. 2,139,845. Boxes where V-grooves are used at fold lines are described, e.g., in U.S. Pat. No. 3,654,053 and U.S. Pat. No. 3,913,822.
A box that is formed of corrugated or similar sheet material with a dado groove and a V-groove to form double-thickness side walls is described in my earlier U.S. Pat. No. 5,337,916, having a common assignee herewith. That patent is incorporated herein by reference. There, the blank is folded up at the V-groove to form a 90-degree fold and at the dado groove to form a 180-degree fold. The outer liner extends continuously over the outside, top edge, and inner side of the resulting double-thickness wall. This technique produces a box with high strength and good crush resistance, both vertically and laterally. The box of this construction provides excellent cushioning to the product that it carries, and avoids or eliminates most of the flexing that is associated with the previous boxes or trays of this type.
The inventor herein has recently discovered that a pair of V-grooves, parallel to each other and with their center lines spaced about two thicknesses of the material, will serve to make the 180 degree bend without use of the dado cut. This produces a somewhat stronger, more rigid top to the double-thickness wall, and has the advantages of the dado and V-groove construction in that the outer liner extends continuously over the bottom, side and top of the sidewall.